Innovative edible films and coatings based on red color pectin obtained from the byproducts of Hibiscus sabdariffa L. for strawberry preservation

Abstract

Edible coatings and films have gained interest because of their benefits to increase shelf life of fresh produce such as fruit and vegetables, while organic residues may constitute alternative sources to extract film-forming materials. Therefore, this research aimed to characterize coatings and films based on an innovative type of pectin obtained from the byproducts of Hibiscus sabdariffa L. (HsL) of the Sudan cultivar, to preserve strawberries. Coatings and films were prepared with HsL pectin (0.8–1.8%) and glycerol (0.5–1.5%) as plasticizer, at different casting volumes (10–20 mL). The characteristic color of HsL calyces remained in film formulations, and the intensity of this was proportional to the amount of pectin. Solutions with pectin percentages as low as 1.3% yielded coatings with high viscosities of 2500.0 ± 35.6 cP, whereas 1.8% pectin notably increase viscosity up to 6707.5 ± 126.5 cP. Films displayed different values of solubility (52.0–90.7%), water vapor permeability (4.0–14.5 × 10–12 g m−1 s−1 Pa−1), and mechanical properties (tensile strength, 1.0–10.6 MPa, elongation at break, 2.8–18.7%, and elastic modulus, 2.3–21.8 MPa), as a function of factors combination. Further, an optimized coating formulation was evaluated on strawberries, which showed a significant (p < 0.05) reduction of weight loss (39.1%) compared to the control (43.8%), during storage for 21 days. Other significant (p < 0.05) parameters were total soluble solids, total anthocyanins, color, and ascorbic acid. On coated fruit, the aerobic plate count decreased, Enterobacteriaceae and coliforms were not significant, and Escherichia coli was below the detection limit; only yeast and mold counts were higher compared with those of the uncoated fruit.